Patients with cerebral stroke in general are often taken to hospitals only after they fall unconscious due to cerebral infarction or cerebral hemorrhage, and such a patient with cerebral stroke receives treatment unavoidably while remaining unconscious. Therefore, a medicament administered for the treatment of such a disease is preferably a preparation suitable for parenteral administration such as an injection. Particularly, in an expectation of rapid expression of the effect, it is preferably an injection for intravenous administration. At present, Radicut (edaravone) and t-PA, which are used as agents for treating cerebral infarction, are all injections for intravenous administration.
Meanwhile, it is well known that the most important factor for a medicament is stability, since such a product is necessarily subjected to a long-term stability test lasting for several months in the development stage. Generally, a chemical substance is more stable in the solid state rather than the liquid state and as a solution in a high concentration rather than that in a low concentration. Thus, even for certain medicaments that should be administered to patients as dilute solutions, many of them are supplied in a more stable form, which can be administered to a patient only after being subjected to the operation of dissolution or dilution at the time of use by means of direct manipulation of a person involved in medical services such as a doctor or a nurse. An injection, in particular, can be stored for longer periods of time and can have more stable quality when it is supplied in the form of a liquid in a high concentration such as an enriched injection or a concentrated injection, or in the solid form such as a lyophilized preparation.
Meanwhile, as examples of an injection comprising (2R)-2-propyloctanoic acid or a salt thereof, which is useful as an agent for treating or preventing various cerebral nerve diseases including cerebral stroke, the injections described in the following have been reported.
A pentanoic acid derivative which is useful as an agent for cerebral function improvement is known to be used as an injection, upon mixing with at least one inert aqueous diluting agent (distilled water for injection, saline, etc.) or at least one inert non-aqueous diluting agent (propylene glycol, polyethylene glycol, etc.) (see, for example, the specifications of EP 0632008 and EP 1174131). These publications describe that an injection can further comprise auxiliaries such as a preservative, a wetting agent, an emulsifier, a dispersing agent, a stabilizing agent and a solubilizing aid.
However, there is not available any known literature that specifically discloses an injection comprising (2R)-2-propyloctanoic acid or a salt thereof, or any report on a medicament comprising (2R)-2-propyloctanoic acid or a salt thereof in a high concentration for the formulation of an injection.